Odd problem with brake lights

I found out today that on my 2006 Tacoma, all three tail lamps work (left, right, and the high mount lamp above the bed on the back of the cab) turn on, but only the brake light on the cab illuminates when I hit the brakes. It's the same light bulb in the taillights for both brake lights and tail lamp functions. Would there be a relay that increases the voltage to the bulbs when the brake pedal is depressed between the cab lights and the taillights that I should check?

 

The bulbs are a dual filament - lower wattage for the tail light, higher wattage for brake light, essentially two bulbs contained in one, thus the three wire connection. In your case the higher wattage filaments are not working - either both are burnt out, or there is an issue with the brake light power to the rear of the truck.

 

This ^^^^^^^^^^^^^

 

Wow, better take it to the dealer to get it looked at

 

Have you tried changing bulbs in the taillights?

 

The OP is asking for help to diagnose the issue, that's one of the benefits of being on a forum. Troubleshooting lights is not that difficult and the OP should explore all options before taking it to a dealer.

 

I had no idea there were two filaments in the bulbs, so yeah, the brake filaments in both bulbs were burned out. In my defense, I checked both with a spare bulb (which, going back and looking, turned out to be a single-filament bulb, so of course that didn't help diagnose the problem), before I posted on here. Same base, but single filament. Also, I've never had two lights go out at the same time, which made me thing the problem was more serious than just burned out bulbs. Thanks!

 

Win-win - you learned something new, and fixed your truck without great expense. Thanks for the update.

 

unlucky BOTH bulbs went bad at the same time...if it happens again then you have some other electrical issues....

 

Just a thought...is it possible that you had one burned out brake light for a while before the other one went out, and you just didn't happen to notice it?
I see that a lot more then people might think, cars and trucks running around with just one brake light working...